Incubation in Poultry Breeding

the hatching of young from the eggs of poultry in incubators. The practice originated more than 2,500 years ago in Egypt and China. Methods of incubation were kept secret for a long time. In Europe attempts to use incubation are known from the 14th century. Owing to the imperfection of incubation apparatus (casks submerged in rotted manure, bakers’ ovens, and so on) and inadequate study of the conditions of incubation, it did not become common. Only since the end of the 19th and beginning of the 20th century, with the invention of better incubators, has incubation become widely used in Europe and the USA; since the middle of the 20th century it has been the principal method of propagating poultry. Incubation makes it possible to hatch large batches of young simultaneously.

In many hatcheries and specialized farms, year-round incubation is practiced, permitting planned replacement of poultry in productive flocks and ensuring even, year-round production of poultry eggs and meat.

The eggs of all types of poultry are incubated: chickens, turkeys, ducks, geese, and guinea fowl. The success of incubation depends on the incubation qualities of the eggs and on the conditions of incubation. The eggs selected for incubation are fresh, biologically perfect eggs from clinically healthy birds that have reached a certain age: chickens, 8–9 months; ducks, 6–7 months; geese, 9–10 months; and turkeys, 8 months. The weight of the eggs must be no less than the average for each type of poultry: no less than 50 g for egg-laying breeds of chickens, 52–53 g for meat and egg-laying breeds of chickens, 70–90 g for turkeys, 80–100 g for ducks, 120–180 g for geese, and 40–45 g for guinea fowl. Eggs of irregular shape or with shell defects, more than one yolk, a displaced, movable, or wandering air cell, foreign inclusions, or other damage are not suitable for incubation.

The length of the incubation period for chicken eggs is 20–22 days; duck eggs, 27–28 days; turkey eggs, 26–28 days; and goose eggs, 29–30 days. The main physical factors in the conditions of incubation are temperature, relative humidity, and chemical composition and rate of circulation of the air in the incubator. The embryos require different conditions during various periods of development; therefore, the conditions of incubation are varied during the course of incubation. Chicken and turkey eggs are incubated at a temperature of 37.4°–37.5°C and a humidity of 54–55 percent; during the last days of the incubation period the temperature is lowered to 36.9°–37°C, and the humidity is increased to 70 percent or more. The conditions of incubation for eggs of water fowl are: a temperature of 37.7°–37.8°C and a humidity of 52–56 percent during the first eight days; then the temperature is lowered to 37.4°–37.5°C and the humidity is decreased to 47–48 percent; during the last days the temperature is maintained at 36.9°–37°C and the humidity is increased to 70–80 percent. The eggs of chickens, turkeys, and ducks are incubated in a vertical position (with the air cell on top), and those of geese are incubated in a slanting or horizontal position. During the entire period of incubation (until transfer to the hatching cabinets) the trays of eggs are automatically turned 90” every two hours; this prevents the embryo and membranes from adhering to the shell and keeps the membranes from growing together. Also practiced is periodic cooling of the eggs, which stimulates oxidative processes and intensifies metabolism in the embryo.

One or two days before the end of the incubation period, the trays of eggs are transferred to the hatching cabinets. Before being transferred for hatching, purebred eggs of definite lines or breeds are placed in separate trays, and for individual accounting of the ancestry of the young, each egg is placed in a separate cubicle. The conditions of incubation are refined on the basis of biological inspection, which permits evaluation of the quality of incubated eggs and establishment of the causes of abnormal development or death of embryos.